1. Field of the Invention
The present invention relates generally to a heat dissipation unit, and more particularly to a heat dissipation unit, which is a combination of a vapor chamber and a heat pipe.
2. Description of the Related Art
There is a trend to develop thinner and thinner electronic apparatuses nowadays. The ultra-thin electronic apparatus includes miniaturized components. The heat generated by the miniaturized components of the electronic apparatus has become a major obstacle to having better performance of the electronic apparatus and system. In order to solve the heat dissipation problem of the components in the electronic apparatuses, various vapor chambers and heat pipes with better heat conduction performance have been developed.
The vapor chamber has a rectangular housing and capillary structures formed on inner wall face of the chamber of the housing. A working fluid is filled in the housing. One face (the evaporation section) of the housing is attached to a heat generation component (such as a central processor or a Northbridge/Southbridge chipset) to absorb the heat generated by the heat generation component. Accordingly, the liquid working fluid in the evaporation section of the housing evaporates into vapor working fluid to transfer the heat to the condensation section of the housing. The vapor working fluid is cooled and condensed into liquid phase. Under gravity or capillary attraction of the capillary structures, the liquid working fluid flows back to the evaporation section for next vapor-liquid circulation. Accordingly, the heat can be spread and dissipated.
The working principle of the heat pipe is similar to that of the vapor chamber. Metal powder is filled into the interior of a hollow circular tube. Then the metal powder is sintered to form an annular capillary structure on inner wall face of the heat pipe. Then the heat pipe is vacuumed and a working fluid is filled into the heat pipe. Finally, the heat pipe is sealed to form the heat pipe structure. The liquid working fluid in the evaporation section of the housing is heated to evaporate into vapor working fluid. The vapor working fluid diffuses to the condensation end to transfer the heat to the condensation end. During the diffusion, the vapor working fluid is gradually cooled and condensed into liquid phase. Under capillary attraction of the capillary structure, the liquid working fluid flows back to the evaporation section for next vapor-liquid circulation.
In comparison with the vapor chamber, the heat pipe conducts heat in a different manner. The vapor chamber serves to two-dimensionally face-to-face transfer heat, while the heat pipe serves to one-dimensionally transfer heat.
Moreover, the conventional vapor chamber can provide heat spreading effect. However, there is a problem existing in the vapor chamber. That is, the vapor chamber transfers heat in such a manner that the vapor chamber absorbs heat from one face to evaporate the working fluid into vapor phase. The vapor working fluid diffuses to the condensation end to transfer the heat to the other face. In other words, the vapor chamber simply transfers heat from one face to the other face to achieve heat spreading effect. The vapor chamber can hardly transfer the absorbed heat to a remote end for dissipating the heat as the heat pipe. Accordingly, the vapor chamber only serves to uniformly face-to-face transfer heat by large area, while failing to transfer heat to a remote end. In the case that the heat is not dissipated in time, the heat will accumulate around the heat source.
Therefore, it has become a critical topic how to improve the current heat dissipation technique and greatly enhance heat transfer efficiency so as to effectively solve the heat dissipation problem of the high-power electronic components.